1. Field of the Invention
Aspects of the present invention relates to a secondary battery and, more particularly to a structure of a battery pack for coupling a secondary battery.
2. Description of the Related Art
Recently, compact, light-weight and portable electronic devices, such as cellular phones, notebook computers, camcorders, and the like, are being developed and produced briskly. These portable electronic devices include a battery pack so that the devices can be operated even where additional power sources are not provided. Currently, the battery pack employs a secondary battery in which charging/discharging can be executed when taking the economic aspects into consideration. A Ni—Cd battery, a Ni-MH battery, a Li battery and a Li-ion secondary battery are examples of typical secondary batteries. The operation voltage of the Li-ion secondary battery is approximately three times higher than those of the Ni—Cd battery and the Ni-MH battery, which are widely used as the power sources of the portable electronic devices. In addition, Li-ion secondary batteries are widely used since the energy density per unit weight for Li-ion secondary batteries is very high.
The secondary battery usually employs a Li-based oxide as positive electrode active material and a carbonic material as negative electrode active material. Generally, the secondary battery is classified into a liquid electrolyte battery and a high-polymer electrolyte battery according to the kind of electrolyte. A battery using the liquid electrolyte is called a lithium ion battery, and a battery using the high-polymer electrolyte is called a lithium polymer battery. A lithium secondary battery is formed in various kinds of shapes, such as a cylindrical shape, a square shape, and a pouch shape.
Among the secondary batteries having these shapes, the edges of the secondary battery in a square shape may be crushed due to shocks during assembly and/or use. In order to prevent this problem, the secondary battery may be used after coupling a cover frame to a battery that covers the edges of the secondary battery.
The secondary battery has a rounded lateral side surface, and thus assembling the secondary battery with the cover frame is difficult due to the lateral rounded side surface. The assembly workers push the battery into the cover frame, and as a result, the cover frame is deformed inelastically. Moreover, because the cover frame does not return to the first shape due to the deformation, reassembling the secondary battery with the cover frame is difficult.
Also, a rounded side surface of the secondary battery with which the cover frame is in contact is depressed, affecting assembling reliability of the cover frame.